Chloro benzyl bromide

Secondary benzylic bromides, allylic bromides, and a-chloro ethers can undergo analogous reactions using ZnBr2 as the catalyst.1 2 Primary iodides react with silyl... 

Alkyl iodides, benzyl chlorides, benzyl bromides, and adamantyl bromides and iodides undergo reduction with triethylsilane/palladium chloride.195 The reduction of a /3-chloro ether occurs in excellent yield with this system (Eq. 56).195... 

Benzylic halides are reduced very easily using complex hydrides. In a-chloroethylbenzene lithium aluminium deuteride replaced the benzylic chlorine by deuterium with inversion of configuration (optical purity 79%) [537]. Borane replaced chlorine and bromine in chloro- and bromodiphenylme-thane, chlorine in chlorotriphenylmethane and bromine in benzyl bromide by hydrogen in 90-96% yields. Benzyl chloride, however, was not reduced [5iSj. Benzylic chlorine and bromine in a jy/n-triazine derivative were hydrogeno-lyzed by sodium iodide in acetic acid in 55% and 89% yields, respectively [5i9]. 

Agemian and Chau [190] have reported a method for determining low levels of 4-chloro-2-methylphenoxyacetic acid and 4-(4-chloro-2-methylphenoxy)-butyric acid in non saline and waste waters by derivatisation with pentafluorobenzyl bromide. The increased sensitivity of the pentafluorobenzyl esters of these two herbicides over the 2-chloroethyl methyl esters as well as their longer retention times make pentafluoro-benzyl bromide the preferred reagent. 

Alkyl halides (particularly bromides) undergo oxidative addition with activated copper powder, prepared from Cu(I) salts with lithium naphthalenide, to give alkylcopper species10. The alkyl halides may be functionalized with ester, nitrile and chloro functions ketone and epoxide functions may also be tolerated in some cases11. The resulting alkylcopper species have been shown to react efficiently with acid chlorides, enones (conjugate addition) and (less efficiently) with primary alkyl iodides and allylic and benzylic bromides (equations 5 and 6). If a suitable ring size can be made, intramolecular reactions with epoxides and ketones are realized. 

Potassium chromate, K2Cr04, is used very rarely. It converts hydra-zomethane into azomethane [613]. In the presence of hexamethylphos-phoramide and crown ether, it transforms allylic and benzylic bromides into a,p-unsaturated aldehydes [614], and in the presence of dilute sulfuric acid, it oxidizes chlorohydroquinone to chloro-p-benzoquinone [615]. 

Problem 25.10 Describe simple chemical tests (if any) that will distinguish between (a) bromobenzene and //-hexyl bromide (b) /7-bromotoIuene and benzyl bromide (c) chlorobenzene and 1-chloro-1-hexene (d) a-(p-bromophenyl)ethyl alcohol (/ -BrC(>H4CHOHCHx) and p-bromo-//-hexylbenzenc (e) a-(p-chlorophenyl)ethyl alcohol and j8-(p-chlorophenyl)ethyl alcohol (/7-CIC6H4CH2CH2OH). Tell exactly whai you would do and see. 

Stepwise alkylations have been carried out successfully with primary alkyl halides, isopropyl iodide, l-chloro-3-iodopropane and benzyl bromide " (Scheme 63, entry b). Other secondary halides and r-butyl halides fail to react. ... 

The proof given in support of dianion formation does not however seem to be sufficients Nevertheless the single step process is reasonably efficient when primary alkyl halides are used but none of the dialkylated compound is produced with isopropyl iodide and benzyl bromide. 2-(o>-Haloalkyl)-l,3-di-thianes have proved to be valuable precursors of 1,3-dithianes derived from cyclic ketoncs. Haloge-nated 1,3-dithianes have been in turn prepared from 2-lithio-l,3-dithiane and stoichiometric amounts of u-chloro- or bromo-alkyl iodides or with an excess of the corresponding dichloride (Scheme 64, entry c). Use of u-bromoalkyldithianes is often impractical because of the ease with which these compounds are transformed into cyclic sulfonium salts. ... 

Treatment of lV-methanesulfonyl-l,4-dihydFopyridine with n-butyllithium, followed by benzyl bromide, leads to the corresponding lV-l-(2-phenylethyl)sulfonyl-l,4-dihydropyridine in low yield. The sulfonamide shown in Scheme 131 (entry c) has proved a valuable c -isoprenoid synthon which allows the two-step C -homologation of allyl halides. This synthon was used for the remarkable two-step stereoselective synthesis of nerol from 3-methyl-2-butenyl chloride (Scheme 131, entry c). Finally, the a-chloro dicarbanion of 4-(a-chlon>methanesulfonyl)morpholine is readily availabl on reaction with 2 equiv. of n-butyllithium in THF, and it leads to the corresponding dimethyl derivative with no detectable monoalkylated product or starting sulfonamide on methylation. Intramolecular versions of these reactions allow the low yield synthesis of neopentyl cyclopropanesulfonate (scheme 131, entry d) and the efficient preparation of cyclopropanesulfomorpholine (scheme 131, entry e). ... 

The rather unreactive arylcadmium reagents, ArCdCl, do react satisfactorily with both primary and secondary a-bromo esters and with secondary allylic bromides, but curiously they react much more poorly with allyl and benzyl bromide, and a-chloro ethers ca. 40% yields) no coupling occurs using primary alkyl bromides. Finally, the old Wurtz-Fittig mediodology, whereby an aryl bromide and an alkyl iodide are coupled in the presence of elemental sodium, can sometimes lead to acceptable yields (40-60%) no rearrangement products are formed, and it is likely that free radicals are not involved. 

When a strong electron-withdrawing group is present in the benzyl halide, e.g. 2-chloro-4-nitro-benzyl bromide (Scheme 7), the normal phase-transfer alkylation will give only ring expansion product (16). However, if the reaction temperature is kept at 0°C, the rearrangement process can be suppressed completely. 

The 3-chloro derivative was developed to impart greater acid stability to the azido-benzyl ether. It is formed using the benzyl bromide (NaH, DMF) and is much more stable to BF3-Ft20, but it is cleaved in neat TFA. Conditions used to cleave the azi-dobenzyl ether also cleave the 4-azido-3-chlorobenzyl ether (Ph3P, THF DDQ, H2O, AcOH, rt, 1 h, 75% yield). The ClAzb ether is inert to DDQ oxidation. ... 

Polystyrene-bound 1-hydroxybenzotriazole (20) [41] (Section 7.3) was originally prepared by Friedel-Crafts alkylation of macroporous polystyrene or copolysty-rene-2% divinylbenzene using 3-nitro-4-chlorobenzyl bromide or 3-nitro-4-chloro-benzyl alcohols in the presence of aluminium trichloride. The so-obtained... 

Conformational analysis " of 3j8-ethoxycarbonyl-3o -phenyltropane, an analogue of pethidine, by n.m.r. spectroscopy, indicated axial preference of the 3a-phenyl group, hence a chair conformation for the piperidine ring (22). However, the intermediates 3a-diphenylhydroxymethyl-3/3-tropanol (23) and 3a-phenyl-3)8-tropanylphenyl ketone (24) favour the boat form. Pyrolysis of (22) led, with the boat form in the transition state, to 7-aza-3-chloro-7-methyl-l-phenyl-8-oxobicyclo[4,2,l]nonane (25), based on elemental analysis and mass spectrum. ( —)-1-p-Butoxyphenyl [a- H]hyoscyaminium bromide was prepared from ( —)-hyoscyamine and p-butoxy[a- H]benzyl bromide. N-Methyl [l- H]- psicaine neu and U-tritiated psicaine have also been described." ... 

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